Phase shifting circuit



June 5, 1951 H. L. KELLOGG ETAL PHASE SHIFTING CIRCUIT 2 Sheets-Sheet 1Filed Jan. 20, 1950 A'IddOS'J'V- O I Inventors: Ham "y L Keilogg, RobertW. Kuehning, by

Th eh" ACtOTT'I ey.

June 5, 1951 H. KELLOGG EI'AL 2, 7

PHASE SHIFTING CIRCUIT Filed Jan. 20, 1950 2 Sheets-Sheet 2 Inventors:

Harry L. KeHogg, Robevt W. Kuenning,

Th e'nr Attorney.

Patented June 5, 1951 PHASE SHIFTING CIRCUIT Harry L. Kellogg, Scotia,and Robert W. Kuenning, Schenectady, N. Y., assignors to GeneralElectric Company, a corporation of New York Application January 20,1950, Serial No. 139,682

- 3 Claims.

. Our invention relates to phase shifting circuits andmore particularlyto phase shifting circuits utilizing magnetic amplification means forcontrolling the degree of phase shift and reactance means for modifyingthe shape of the alternating current wav together with resistance meansfor increasing the speed of response of the circuit and for improvingthe shape of the alternating voltage wave.

In electric discharge devices of the ignitron type wherein a mercurypool cathode and an ignitor for initiating electronic emission at thecathode are used, it is necessary that the electric energy supplied tothe ignitor be timed precisely in order that the device can be properlycontrolled and it is the practice to adjust the phase relation of theignitor firing circuit by various types of phase shifting circuits. Mostknown phase shiftin circuits are either too slow in response or tend toproduce wave shapes which are greatly distorted from the desiredsinusoidal wave shape, or require excessive control power.

An object of our invention is to provide an improved phase shiftingcircuit wherein the current and voltage waves are not appreciablydistorted.

Another object of our invention is the provision of an improved phaseshifting circuit wherein effective and prompt response are possible.

Still another object of our invention is to pro vide an improved phaseshifting circuit utilizing magnetic amplification means for controllingthe degree of phase shift and wherein means are provided for modifyingthe wave shapes produced thereby so that such waves are substantiallysinusoidal.

The invention utilizes a magnetic amplifier having a pair of conductingcoils arranged in parallel together with a unidirectional conductingdevice arranged in series with each of these coils to supply each halfcycle of current to a load circuit from an alternating current supplycircuit. A control winding energized with direct current is used toeffect variations in the degree of saturation of the amplifier. Inaccordance with the present invention, resistance means is arranged inseries with each of the coils of the amplifier to increase the speed ofresponse of the circuit and to improve the shape of the voltage outputWave andreactance means is arranged in parallel with the amplifier coilsto improve the shape of the current output wave.

Fora better understanding of our invention reference may be had to theaccompanying drawings in which Fig. 1 is a schematic representation ofour invention as embodied in a firing circuit for ignitor elements usedto initiate a cathode spot in an electric discharge device of theignitron type; Fig. 2 is a family of curves showing the phaserelationship between certain voltages and currents together with thewave shape thereof when the magnetic amplifier is adjusted so that itsimpedance is high in magnitude; Fig. 3 is a family of curves similar toFig. 2 and represents the condition when the impedance of the magneticamplifier is adjusted to a low magnitude; Figs. 4 and 5 are similar toFigs. 2 and 3 and represent conditions obtaining when the impedance ofthe amplifier is adjusted to an intermediate valve.

Fig. 1 shows our invention as applied to the ignitor firing circuit of apair of ignitron tubes I and 2. Ignitrons l and 2 are respectivelyprovided with plate elements 3 and 4, control grids 5 and 6, holdinganodes l and 8, ignitors 9 and I0 which are respectively immersed inmercury pools ll and I2 which respectively form the cathodes of tubes Iand 2. Ignitor 9 is energized through unidirectional conducting deviceFMRI from a secondary winding of ignitor coupling transformer ICT.Ignitor ll! of tube 2 is energized through unidirectional conductingdevice FMR.2 from a secondary winding of transformer ICT. The primaryWinding of transioremr ICT is energized from a phase shifting networkgenerally indicated by the numeral l3 through the circuit comprisinglinear reactor LL, saturable reactors FLl and FL2 and the capacitorelements FCI and F02.

As is disclosed and claimed in United States Patent 2,523,027 grantedupon an application of B. D. Bedford and H. L. Kellogg and assigned tothe assignee of this invention the saturable reactors FLI and FL2 arearranged so that the voltage rating of reactor FLI is substantiallygreater than that of reactor FL2. Also the impedance of saturablereactor FLI when saturated is substantially greater than the impedanceof reactor FLZ when saturated. Thus a charge from the alternatingcurrent supply is supplied to capacitor FCI through the phase shiftnetwork l3 and subsequently this charge on capacitor FCI is dischargedinto capacitor F02 through reactor FLI. Likewise, the charge accumulatedon capacitor F02 is subsequently discharged to the primary winding oftransformer IC'I through reactor FLZ. Since the impedance of reactor FL2is considerably less when that reactor is saturated than is theimpedance of reactor FLl when saturated, the flow of current fromcapacitor F02 to the primary winding of transformer ICT is much greaterthan the current flow from capacitor FCI through reactor FLI and intocapacitor F02. In this way, a concentrated energy flow of relativelylarge power is supplied to ignitor 9 without appreciably impairing thevoltage supplied to the ignitor andthe component parts of the ignitorfiring circuit can be constructed of much smaller physical size than inprevious ignitor firing circuits.

The phase shiftin arrangement l3 comprising our invention is providedwith a winding ['4 in parallel with a winding 55. A resistor r'i a'n'd-aunidirectional conducting device 16 are arranged in series with respectto winding 14 and a resistor n as well as unidirectional conductingdevice H are arranged in series with the winding I5. Thus, it will beobvious that whatever the polarity of the alternating current suppliedto the terminals I 8 and i9 may be at any instant, current will becaused to flow through the wind: ing [4 in the direction of the arrowduring half cycles when terminal 18 is positive but not when thatterminal is negative due to theaction of unidirectional conductingdevice l6. When terminal I8 is negative, current will flow throughWinding l in the direction indicated by the arrow but, due to the actionof unidirectional conducting device I'l, current will not flow throughwinding 15 when terminal 18 is positive.

For the purpose of adjusting the degree of saturation of the windings l4and [5, a source of direct current 20 is used to supply to controlwindin 2|, a direct current bias which is adjustable by means of thedevice 22. Since the winding 21 conducts direct current and since theflux established by the windings Hi and I5 is always in the samedirection, the portion 2 la. of winding '2! and the portion 21b ofwinding 2| may be wound in-such a direction that the bias from source 20will either oppose or augment the fiuxof both windings l4 and i5 due tothe flow of current therethrough from the alternating current sourceterminals l8 and 1-9. The polarity of source 20 can be reversed ifdesired by known potentiometer means.

Those portions of the network [3 described thus far canbe adjusted sothat the impedance of each of the windings l4 and I5 isnormally of avery high or very low value by suitable adjustment in thedevice 22. Forexample, a bias could be applied to windings l4 and I5 which would causethese windings to afiord a very high or a very low impedance to the flowof current therethrough. By the same token an intermediate bias may bechosen so that a current of intermediate proportions in control Winding2| will cause saturation of the windings f4 and 15 only when aided bythe voltage applied to coils l4 and i 5 from source Iii-4'9 to effect asubstantial reduction in the impedance of these windings during only aportion of each cycle.

The reactor CL and capacitor PC of Fig. 1 are for the purpose ofObtaining the desired power factor and also act to improve the waveshape in accordance with known principles.

Fig. 2 is representative of certain voltage and current relationshipsexisting when the windings i l and I 5 are adjusted to afford a veryhigh value of impedance such that the voltage available is insufficientto cause saturation of coils l4 and I5. In Fig. 2 the supply voltage atterminals I8 and IQ of Fig. 1 is represented by the curve Es. thevoltage applied between terminal [9 and the The voltage represented bythe curve Ercis direction of r'ectifiers l6 and -l'!.

source terminal of linear reactor LL and the angle 9 represents thephase shift accomplished by the network [3. The current supplied by thevoltage Em to the firing circuit is represented by the curve Ifc and isshown lagging the voltage Efc by a small angle. The voltage whichappears across the reactance R, shown in Fig. 1 is represented by thecurve in Fig. 2 designated ER.

The phase shift angle may be reduced by adjusting device 22 so as toincrease the saturation of windings l4 and I5 by the action of currentflowing through control winding 2|. In this way, the impedance ofwindings l4 and I5 can be reduced to arelatively low value due tosaturation and under such conditions, the various relationships may berepresented by the curves shown in Fig. 3. It will be observed that thephase shift angle 9' is relatively small under these conditions. FromFigs. 2 and 3, it will be observedth-a-t the shape of the voltage waves-Efc and of the current waves Ifc are substantially sinusoidal and henceare suitable for energizing an ignitor firing circuit.

If the current supplied to winding "2| is adjusted to some intermediatevalue, the voltage and current waves of the quantities Efc and he areconsiderably distorted due to the occurrence of the saturated conditionat some point on the voltage ES intermediate its maximum and zero valuesso as to render thenetwork l3 unsuitable for use in ignitor firingcircuit if the reactor R and the resistors 11 and r; are omitted. -Inaccordance with our invention, these resistors n and 1' and the reactorR are utilized to render the voltage and current waves supplied to thefiring circuit through the network 13 substantially sinusoidal forintermediate values of current in control winding 2|.

Fig. 4 respresents the improvement in the shope of the voltage wavedueto the action of resistors T and 12. In Fig. 4, the solid line curveEs represents the voltage at terminals '[8 and 19 as in Figs. 2 and 3.The solid line voltage Ema represents the voltage drop of themagneticamplifier coils l4 and I5. It will be obvious that at a predeterminedpoint such as point X on the waveEs'the windings of the magneticamplifier suddenly become saturated and the voltage wave Ema is-suddenlyreduced bye. substantial amount. A wave shape of voltage such asthatrepresented by the curve Emain Fig. 4 is not suitable for use inconjunction with ignitor-firing circuits. In 'orderto prevent thissudden decrease i'nthe voltage Ema, "a supplementary voltage is"supplied which can be'repre's'ented by the cross-hatched areasdesignated in and in in Fig. 4. 'This'voltage is the voltage drop"respectively through the resistors TrandTfWhiCh drop produces "anessentially Sinusoidal wave formro'r'vouage Ere when combined with"those portions of the cycle of the voltage Ems 'Whi'char'eparticularlydistorted. 'In

Fig. 4, the-curve ima represents the current of'the magnetic amplifierand, of'course, one-half cycle of this current would now through "thewinding 54 and the other'h'alf 'cyc'le would flow through the winding[5. Resistors 1'1 "and r2 also'act to increase the speed -of phase shiftupon sudden ly changingthe current in winding-2| in such a direction asto inducea circulating current inthe loopcomprising windings l4 and I5,resistors 1-1 and 12, and rectifiers l6 and I1 in=theconductingResistors 11 and r2 act to reduce themagnitude of this inrapidly so thatthe current in winding 21 is effective in controlling the saturation ofwindings l4 and I5. Otherwise the induced circulatin current would delaythe effect of the change in current in winding 2|.

Fig. 5 also shows the current of im of Fig. 4 and it will be observedthat there is a considerable period of time as represented by thedistance yz during which the current is substantially zero. This wouldresult in the flow of a pulsating current to the ignitor firing circuitwhich current would not be suitable for this purpose. Reactance R isconnected in parallel with the windings l4 and I5 for the purpose ofsmoothing the current Wave. In Fig. 5, the current in which is thecurrent through reactor R is substantially sinusoidal in shape. Thus,the addition of each half cycle of the current ima to the current wavein results in a current wave Ifc which approaches a sinusoidal shape atleast to a degree sufiicient that the network l'3 can be used as aneffective phase shift device without undue distortion of the currentwave.

Experimental work which has been conducted shows that the impedance ofthe reactor R should be 1200 Ohms and that the resistance of resistors nand r2 should be 40 ohms for a particular arrangement wherein theimpedance of windings l4 and I5 is variable from approximately 100 ohmsto approximately 1000 ohms.

While there has been shown and described particular embodiments of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from theinvention in its broader aspects and it is, therefore, intended in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A phase shifting circuit arranged to energize a load and comprising asource of alternating current, a pair of windings arranged in parallel,resistance means and unidirectional conducting means arranged in serieswith each of said windings, said windings, resistance means andconducting means being energized from said source and said conductingmeans being connected to allow alternate half cycles of electric currentto flow therethrough, means for regulating adjusted to a value ofimpedance such that each of said windings is saturated at apredetermined instantaneous value of the voltage of said source.

2. A phase shifting circuit arranged to energize a load and comprising apair of windings arranged in parallel, resistance means andunidirectional conducting means arranged in series with each of saidwindings, said conducting means being connected to allow alternate halfcycles of electric current to fiow therethrough, means for regulatingthe impedance of said windings, said resistance means having a value ofresistance sufficient to prevent a substantial decrease in theinstantaneous value of the voltage across said windings and saidresistance means when said windings are adjusted for a value ofimpedance intermediate the minimum and maximum values thereof, andreactance means arranged in parallel with said windings and theassociated resistance and unidirectional conducting means for supplyingto the load a current the instantaneous values of which are such thatthe,-

total instantaneous values of current supplied to the load by saidwindings and by said reactance means result in a substantiallysinusoidal composite current.

8. A phase shifting circuit arranged to energize a load and comprising apair of windings arranged in parallel, resistance mean andunidirectional conducting means arranged in series with each of saidwindings, said conducting means being connected to allow alternate halfcycles of electric current to flow therethrough, current responsecontrol means for regulating the impedance of said windings, saidresistance means being effective to limit the flow of in ducedcirculating current in the loop including said windings and saidconducting means due to a relatively fast change in current controllingsaid control means, and reactance means arranged in parallel with saidwindings and the associated resistance and unidirectional conductingmeans for supplying to the load a current the instantaneous values ofwhich are such that the total instantaneous values of current suppliedto the load by said windings and by said reactance means result in asubstantially sinusoidal composite current.

HARRY L. KELLOGG. 1 ROBERT W. KUENNING- REFERENCES CITED UNITED STATESPATENTS Name Date Mittag Nov. 7, 1944 Number

